Soybean sauce koji, preparation method thereof and soy sauce

The invention provides a preparation method of soy sauce koji, which comprises the following steps: A) mixing bean dregs, bran, flour and water to obtain a mixed culture medium; and B) sterilizing the mixed culture medium, inoculating yeast seeds, and carrying out continuous aerated culture, the ventilatory capacity of the aerobic culture is 3-5 m < 3 >/h, and the air pressure is 0.4-0.6 Mpa. The invention provides the water-replenishing-free mold starter culture process, the operation is simple, the waste of equipment, manpower, materials, water, electricity and gas required by mold starter water replenishing and humidifying is reduced, and the single-tray spreading thickness is increased, so that the mold starter productivity and efficiency are improved. The storage period of the mold starter cultured by the method can be prolonged to 30 days or more from the original 1-2 days. The production inoculum size of the prepared koji can be reduced by 30%, the prepared koji and soy sauce are low in infectious micr